Someone asked about having first class declassified on a packed train. Twitter staff rightly said it was the job of the onboard staff to do that.
After that @mtinge ask this:
https://twitter.com/mtinge/status/827214770633838592
Have does it work for Thameslink?
I was on a short-formed train which did not appear to have an OBS on board, and the drivers announcement was along the lines of "Please move as much as possible into the train, first class... well don't worry about first class, please move inside the train".